/*
 * #%L
 * %%
 * Copyright (C) 2015 Trustsystems Desenvolvimento de Sistemas, LTDA.
 * %%
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * 3. Neither the name of the Trustsystems Desenvolvimento de Sistemas, LTDA. nor the names of its contributors
 *    may be used to endorse or promote products derived from this software without
 *    specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * #L%
 */
package com.tompai.elfinder.support.concurrency;

import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;

public class GenericCache<K, V> {

	private final ConcurrentMap<K, Future<V>> cache = new ConcurrentHashMap<>();

	private Future<V> createFutureIfAbsent(final K key, final Callable<V> callable) {
		Future<V> future = cache.get(key);
		if (future == null) {
			final FutureTask<V> futureTask = new FutureTask<>(callable);
			future = cache.putIfAbsent(key, futureTask);
			if (future == null) {
				future = futureTask;
				futureTask.run();
			}
		}
		return future;
	}

	public V getValue(final K key, final Callable<V> callable) throws InterruptedException, ExecutionException {
		try {
			final Future<V> future = createFutureIfAbsent(key, callable);
			return future.get();
		} catch (final InterruptedException | ExecutionException | RuntimeException e) {
			cache.remove(key);
			throw e;
		}
	}

	public void setValueIfAbsent(final K key, final V value) {
		createFutureIfAbsent(key, new Callable<V>() {
			@Override
			public V call() throws Exception {
				return value;
			}
		});
	}

	public void removeValue(final K key) {
		cache.remove(key);
	}
}
